1. Field of Invention
This invention relates to posture assessment and feedback instruments that respond to bending and curvature.
2. Description of Prior Art
This invention relates to a posture feedback instrument designed to prevent slumped posture and the associated ailments. In order to achieve this task successfully, a posture feedback instrument needs to be reliable, user-friendly, inexpensive and durable. A single inclination sensor as used in U.S. Pat. No. 6,877,240 (2005) cannot differentiate slumping from leaning forward with a straight back, while a multitude of sensors would make the process expensive and less user-friendly. Therefore, a reliable assessment of slumped posture requires a sensor that is sensitive to curvature rather than inclination.
Amongst the curvature sensing prior art, U.S. Pat. No. 6,673,027 (2004) was turned into a commercially available posture feedback instrument. Studies showed it to function reliably and effectively. It is also user-friendly in the sense that its application to the xyphoid area can be accomplished independently and does not impede activities of daily living such as leaning against a back rest.
The main deficiencies of the embodiment of U.S. Pat. No. 6,673,027 are caused by the design of its sensor. The sensor is composed of a signal source and a receiver element connected by a moveable hardware component. Manufacturing the moveable hardware component with the required precision turned out to be a complex and costly process. The moveable component has also turned out to be the least durable one. It is the only part that has ever required replacement after breaking in a number of cases. Its fragility also made it less user-friendly, because it required the users to read the manual and treat the sensor with care. Finally, cleaning moveable components for functional, aesthetic, and cleaning purposes is cumbersome.
Therefore, a curvature sensing solution was sought in which the user-friendly and effective application of a single sensor to the xyphoid area could be preserved, while eliminating the moveable hardware component.
The solution was found by replacing the separate signal source and the moveable hardware component of U.S. Pat No. 6,673,027 with a capacitive sensor. A typical capacitive sensor creates an electric field between two metal traces on a piece of circuit board. When the field is invaded by a human body, the sensor output changes according to how close the body gets. This makes the proximity of the body the input variable, rather than the distance between a signal source and a receiver. Thus a capacitive sensor eliminates the need for a signal source that can move in relation to its receiver.
The only prior art use of a capacitive sensor in the context of posture assessment was found in the sign language recognition apparatus of U.S. Pat. No. 7,565,295 (2009), where a capacitive sensor as a part of an accelerometer was used to measure the acceleration of the signing fingers rather than their curvature.
No prior art was found in which the sensing means for curvature of the spine or other joints was capacitive.
The alternative sensing means used for this purpose in the prior art all suffer from at least one of the following disadvantages:
Sensing means like the ones used in U.S. Pat. No. 5,433,201 (1995) require a receiver and a separate signal source. In order to power the separate signal source, it needs to be connected to the power source via a cable. The separate signal source and the cable connection complicate the handling and the production of the sensing means.
Sensing means like the ones used in U.S. patent application 20080319364 (2008), U.S. Pat. No. 6,673,027 (2004), U.S. Pat. No. 5,143,088 (1992) or U.S. Pat. No. 4,007,733 (1977) require a moveable piece of hardware, compromising the durability of the sensor and making it more difficult to clean. The moveable piece of hardware needs to be crafted with precision, so that it will move easily but without slack, thus adding to production costs.
Sensing means like the ones used in U.S. Pat. No. 5,433,201 (1995) may only be applied to the skin and won't function when applied to the clothes, where the operation and demonstration of sensing means is easier and where there is less sweating between a sensor and the body.
Sensing means like the ones used in U.S. Pat. Nos. 5,433,201 (1995), 6,673,027 (2004) or 5,533,531 (1996) do not allow an embodiment where the entire posture feedback instrument is contained within a single housing.
Sensing means like the ones used in U.S. Pat. Nos. 6,827,694 (2004) or 5,143,088 (1992) do not allow a user-friendly application to the xyphoid area, where it can be reached and handled by a user, while not being in the way when using a back rest.